THISTLE FAMILY 261 



Biennials; heads mostly erect; outer bracts acute. 



Plant glabrous or nearly so. 4. A. caudata. 



Plant decidedly pubescent. 5. A. Forwoodii. 



Perennials, with a rootstock or caudex; heads nodding at least at first. 

 Plant .3-10 dm. liigh; stem leafy. 



Stem tall, very leafy, 4-10 dm. high; bracts acute or acutish. 



6. ,4. pacifica. 

 Stem lower, 3-5 dm. high; stem-leaves rather small and scattered; bracts 

 obtuse or rounded at the apex. 7. A. camp or um. 



Plant less than 1 dm. high; stem scapiform; stem-leaves minute. 



18. A. minuta. 

 Heads larger, 4-5 mm. broad, not very numerous (except in A. Bourgeauana) , in narrow 

 spike-like panicles: plants low, rarely .3 dm. high. 

 Involucral bracts glabrous or nearly so; disk-corollas glabrous. 



8. A. MacCallae. 

 Involucral bracts more or less villous ; disk-corollas tisually with a few hairs on the 



lobes. 

 Plant 3-4 dm. high; heads very numerous, in a dense panicle. 



9. A. Bourgeauana. 

 Plant 1-3 dm. lilgh; heads fewer, usually a spike-like panicle or racemose. 



10. A. spilhamaea. 



II. FlLIFOLl.\E. 



Taller shrubs, 3-10 dm. high, with numerous heads in leafy panicles; heads 3-7-flowered. 



11. A. niifolia. 



Low undershrubs, less than 1.5 dm. high, with racemose inflorescence; heads 10-15- 

 flowered. 

 Leaves ternate or biternate. 12. A. pedalifida. 



Leaves pinnatlfid with 5-7 divisions. 18. .4. minuta. 



III. Frigidae. 



Plant tall, 6-10 dm. high, erect; leaves twice or thrice pinnatifld. 13. A. Absinthium. 

 Plant lower, 2-4 dm. high, often decumbent at base; leaves twice ternate. 



14. A. frigida. 



IV. Lan.\tae. 



Basal leaves twice pinnatifld into linear divisions; stem-leaves pinnate; heads .5-12. 



15. A. scopulorum. 

 Basal leaves pinnatifld into 3-5 linear-oblanceolate approximate divisions; stem-leaves 



ternately cleft or entire; heads 1-4. 16. .4. Pattersoni. 



V. Annuae. 



One species. 17. A. biennis. 



VI. NORVEGICAE. 



Heads 6-10 mm. broad, iisually more than 40-flowered; corollas hairy or rarely glabrous; 

 bracts with fuscous margins. 

 Plant more or less pubescent, at least on the leaves and peduncles. 



Plant silvery-silky; basal leaves 6 cm. long or less, pinnatifld or bipinnatifld with 

 few di^^sions. 

 Plant less than 1 dm. high; leaves 1-1.5 cm. long; involucral bracts with in- 

 conspicuous light brown margins, slightly tomentose, soon glabrous. 



18. A. minuta. 

 Plant 1-3 dm. high; leaves 2-6 cm. long; involucral bracts %vith consnicuous 

 dark brown or blackish scarious margins. 19. A. Tyrrellii. 



Plant green; leaves twice pinnatifld, the basal ones more than 1 cm. long. 



Leaves and stem decidedly hairy; inner bracts ovate, acute, with narrowly 



lanceolate green center. 20. A. saxicola. 



Leaves sparingly pubescent or glabrate; stem glabrous or nearly so; inner 

 bracts obovate, obtuse or rarely acutish, ^vith broadly lanceolate green 

 center. 2l. A. arclica. 



Plant glabrous. 22. A laevigata. 



Heads 5-6 mm. broad, 30-40-flowered ; corolla glandular-granuliferous ; plant glabrous; 

 bracts with light brown margins. 23. A. Parryi. 



VII. Franserioides. 

 One species. 24. A. franserioides. 



VIII. VULG.^RES. 



Leaf-segments again divided or lobed. 



Inflorescence much branched, pyramidal; heads very numerous; involucre campanu- 

 late, 4 mm. high, 10-30-flowered; leaf-segments obovate in outline. 



25. A. vulgaris. 

 Inflorescence narrow, cylindric; heads fewer; involucre hemispheric, 3 mm. liigh, 25- 

 35-flowered; leaf-segments lanceolate, short, acute. 26. A. incompta. 



Leaves or their segments entire or nearly so. 



Heads not very numerous, comparatively large, 25-50-flowered ; involucre hemis- 

 pheric. 

 Inflorescence spike-lUie; suffruticose with a woody base; leaves coarse-toothed. 



28. A. Leibergii. 

 Inflorescence open-paniculate. 



Leaves lanceolate, thui, deeply lobed; involucre glabrous or nearly so. 



27. A. claiior. 



